The study site was a Macadamia orchard, planted in 1988, located near Newrybar, NSW, Australia. It is located in a region of New South Wales colloquially known as “the Big Scrub”. Prior to European settlement, the region encompassed the largest area of subtropical rainforest in Australia. In the 19^th century, extensive timber-getting and clearing for agriculture took place; consequently, remnant rainforest is patchy and a number of rainforest regeneration projects are underway. The region is recognised as a biodiversity hotspot by the Australian Government Department of Environment and Energy. Parts of the orchard have a closed canopy and moist soil with abundant moss and other epiphytes on the macadamia trees. The northwest corner of the orchard has the most complete canopy, most epiphytes and dampest soil. The orchard where D. biseriata were observed was sprayed with pesticide (dipterex 500 sl) between 11^th and 16^th September 2015. This appeared to have no effect on subsequent emergences of pharate adults.

Observations of adult eclosion were made between 5^th to 22^nd September 2015 and from 17^th to 24^th September 2016. Mature adults and pharate adults were collected on and after 5^th September 2015.

Some adults were kept in captivity (in petri dishes or insect containers) while others were killed and pinned. Pharate adults were preserved in ethanol.

Both field and studio photographs were taken, with studio images being of both live and preserved specimens. To record larval morphology, ethanol-preserved first instars were washed in water and cleared in KOH before slide-mounting and photomicroscopy.

For the timelapse observations of adult eclosion, a Canon EOS 60D dSLR camera with 100 mm macro lens was mounted on a tripod and focused on a pharate adult and 759 images were taken over a period of 43 minutes. The camera was controlled by an external remote control and a canon speedlite 580EX II was used to light the specimen. A video was produced comprising of all 759 images played at 25 frames per second.

As far as the authors are aware, mass, near-synchronous emergence of mantispids is a previously unreported phenomenon. It is uncertain if the emergence in such large numbers is a natural occurrence or an artefact of monoculture farming. Adults and exuviae were observed in other local Macadamia orchards at around the same time as the emergence near Newrybar (pers. comm. Jarah Coates and Ken Dorey) and emergence was observed simultaneously in nearby regenerated rainforest, suggesting that emergence is highly seasonal over the local area, perhaps through detection of photoperiod or some attribute of their yet-unknown food source, and that the life cycle covers a single year. Further, the presence in rainforest as well as in a location within the orchard with high soil moisture, dense canopy cover and numerous epiphytes hints at a rainforest association. The much higher prevalence of emergence in the Macadamia orchard compared to nearby regenerating rainforest could be due to more favourable conditions in the Macadamia orchard. It is possible that the coordinated emergence of D. biseriata facilitates mating because at least one of the females collected at the site produced fertile eggs. The species might not just be associated with rainforest; reports suggest that it is also common at the same time of year in open eucalyptus forest.

Pharate adults are remarkably mobile. They use negative geotaxis, possibly combined with visual orientation, to detect and move upward on a tree-trunk or other vertical object before becoming immobile and initiating eclosion behaviour. In Mantispidae, pupation generally takes place within a silken cocoon in a concealed location and the pharate adults leave the cocoon and walk some distance away before eclosing (Redborg 1998). In the Symphrasinae, pharate adults have been reported to emerge from the cocoon within nests of hymenopteran hosts from where they wander or are removed from the hive before they become immobile and eclose (Buys 2008, Maia-Silva et al. 2013). More widely, exarate pupae with mobile pharate stages are the norm in the clade Neuropterida (Kristensen 1999). In the raphidiopteran, Raphidia bicolor, motile pharate adults climb and face upwards on a vertical surface prior to eclosion (Kovarik et al. 1991). In the small, archaic family, Berothidae, sister family to the Mantispidae (Winterton et al. 2010), motile pharate adults were observed to break out of the cocoon and climb away to undergo the final ecdysis (Brushwein 1987). In the present case, cocoons were not observed but they would most likely be underground. The behaviours associated with adult emergence are typical of the Neuropterida with pharate adults tending to grasp a vertical substrate and adopt a posture that presumably allows the wings to expand and harden, as also seen in the Raphidophorid, Raphidia bicolor (Kovarik et al. 1991). The agility and behavioural repertoire of the pupa add substance to Kristensen's (Kristensen 1999) observations that the the motile, exarate, decticous pupae of related, basal endopterygotes—Aspoeck et al. (2012) called them "running pupae"—are substantially different to the compact, mostly inert pupal form of more derived endopterygotes.

The cluster of eggs suspended on silken threads is similar to the egg batch deposited by Lomamyia lattipennis (Berothidae) (Brushwein 1987, Toschi 1964). In one instance, larvae of D. biseriata were obtained by the same means: a captive female laying a batch of eggs that hatched (Winterton, personal communication). Larval morphology was not detailed but it was noted that they lacked stemmata (Winterton et al. 2010), an observation supported by this work. The newly hatched first instar larvae of D. biseriata are campodeiform and mobile with straight, anteriorly-directed mouthparts. Morphologically, they resemble the first instar larvae of other subfamilies of Mantispidae (Hoffman and Brushwein 1992) and the Berothidae (Hörnschemeyer 2013, Wedmann et al. 2013). Comparing the D. biseriata larva to larvae of Mantispinae (Hoffman and Brushwein 1992), the overall body shape and the head of D. biseriata are less robust and more elongate. Another difference is that D. biseriata has none of the pigmentation and sclerotisation usually seen in first instars of Mantispinae (Hoffman and Brushwein 1992, Redborg 1998, Redborg and MacLeod 1984). Distinctive features of the D. biseriata head include the elongate mouthparts and the lobulate rather than elongate terminal antennomeres and palpomeres. In head and mouthpart structure, as well as overall body shape, they resemble larval Berothidae (Wedmann et al. 2013), whose larvae appear to be specialist termite predators (Tauber and Tauber 1968). The antennae are not as slender and the terminal antennal sensillum is not as well developed as seen in fossil and extant Berothidae (Gurney 1947, Hörnschemeyer 2013, Toschi 1964).

Together, the behaviour and morphology of larvae, including their lack of stemmata, their tendency to drop from the egg and burrow into soil, and the subterranean origin of the pharate adults, support the premise that the larval and pupal stages of D. biseriata are subterranean. If this life history was common to all or most Drepanicinae, it could explain the lack of historical knowledge about the immature stages of the subfamily. The larval diet remains unknown; they could be subterranean arthropod predators like the subfamilies Symphrasinae and Calomantispinae or spider-egg predators like their sister sub-family, Mantispinae. A clue, at least in this species, might lie in the apparent preference for moist soil and the rainforest association. Future studies could focus on taking soil samples in the orchard to determine what potential prey or host species are present and possibly to detect larvae or pupae in situ.